Magnetic safety gate



Aug. 24, 1954 w. D. CROZIER MAGNETIC SAFETY GATE 3 Sheets-Sheet 1 Filed Aug. 14, 1950 INVENTOR.

YWILLIAM D. CROZIER B I Xxfl 6&

ATTORNEY 4, 1954 w. D. CROZIER 2,68?,94

MAGNETIC SAFETY GATE Filed Aug. 14, 1950 3 Sheets-Sheet 2 FIG. .2

' INVENTOR.

WILLIAM O. CROZIER ATTORNEY g 9 1954 w. D. CROZIER 2,687,094

MAGNETIC SAFETY GATE Filed Aug. 14. 1950 3 Sheets-Sheet 5 FIG. 4 FIG. 5

JINVENTOR. F 6 WILLIAM Ii CROZIER ATTORN'Y Patented Aug. 24, 1954 MAGNETIC SAFETY GATE William D. Orozier, Socorro, N. Mex., assignor to the United States of America as represented by the Secretary of the Navy Application August 14, 1950, Serial No. 179,103

The present invention relates to a safety device for preventing premature detonation of a shell or other explosive projectile which is to be subjected to static firing.

Static firing is detonation of a shell while it is stationary and is done for various testing and development purposes. The detonation is accomplished by passing an electric current through a squib or other electrical detonator in the fuze of the shell, by means of conductors connected to a remote-control station. Premature firing of the squib may be caused by any one of several conditions, such as a static charge on the lines leading to the remote-control station, a battery inadvertently left in the circuit, and a lightning discharge in the vicinity.'

An object of the present invention, therefore, is to provide safety means for preventing detonation of the explosive charge in the shell in the event of premature firing of the squib.

A more specific object is to provide safety means that normally prevent detonation of the shell and that will keep the fuze unarmed unless a sufficiently intense and prolonged electrical discharge is intentionally fed to the safety means to arm the fuze.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is an axial section through a projectile fuze, modified for use in static firing, and embodying a safety device according to the invention, a fragment of the projectile being shown;

Fig. 2 is a rear end elevation of the safety device, on a larger scale, and shown with its rotor in the armed position;

Fig. 3 is a corresponding view, partly in section, and with the rotor in the unarmed .position;

Fig. 4 is a section through the safety device, in the plane indicated by line 4--4 of Fig. 2;

Fig. 5 is a corresponding side elevation; and

Fig. 6 is a fragmentary axial section through the rear portion of the fuze, on a slightly smaller scale than Figs. 2-5.

Referring first to Fig. 1, there is shown a fuze designated as a whole by reference character It], said fuze having a nose portion II and a body portion l2. Normally these portions of a fuze would be occupied by elements designed to cause the fuze to detonate a shell upon proximity to or contact with a target, but as such elements 10 Claims. (Cl. 10270.2)

are unnecessary in static firing, the present fuze contains merely an axially bored slidably fitting filler block l3, which may be made of ,wood, with a resilient washer M to bear against the block l3 and cause said block in turn to hold the remaining fuze parts in place. The bore 9 in said block afiords a convenient passage for wires which will be described hereinafter.

The said fuze parts comprise a rear fitting and detonator IS, a magnetic safety gate H, which embodies the invention, and an insulating disk I6 between the detonator and the safety gate, and an auxiliary detonator or booster IS. The body portion 2 of the fuze extends into the shell casing l9, to which it is secured by the screw threads 20, which also serve to hold the nose portion H to the body portion.

The details of the magnetic safety gate I! will now be described with reference to Figs. 2 to 6. A flat circular base 2| of non-magnetic material supports the structural parts of this gate. An axial bore 22 extends nearly through the base 2|, leaving a thin frangible portion 23 at its rear end. A shallow recess is formed in the forward face of the base 2|, and accommodates a recessed insulator plate 24 which in turn holds a metal ring 25, as shown.

A shaft 26 may be secured to the base 2|, as by a press fit in a bore 21 or in any other way, and serves as a pivot for a rotor 28 made of suitable ferro-magnetic material, such as soft steel. A sp-iral spring 29 has one end secured to the shaft 26, and the other end secured to the rotor 28, as by inserting said ends in corresponding holes, the said spring normally tending to rotate the rotor counter-clockwise, as seen in Fig. 2. The spring 29 is accommodated in a recess 30 in the rotor, as shown in Figs. 2, 3 and 4.

The rotor 28 is basically cylindrical but has a periphery shaped as shown in Figs. 2 and 3. Two opposite portions are of full diameter, as shown at 3| and 32, and each of these extends through approximately of arc. Two other portions, however, are partly cut away, namely, portion 33 of reduced radius, and ortion 34 opposite said portion 33, which as shown is concave. A stud 35 is mounted in the base 2|, preferably by press-fitting it into a bore 36, as best shown in Fig. 4. This stud serves as a stop for preventing rotation of the rotor 28 beyond the limits set by contact of the opposite ends of the concave portion 34 with said stud, as seen best in Figs. 2 and 3.

A stator, indicated as a whole by reference character 31, comprises a built up core including a yoke 38 and two opposed pole pieces 40 and 4| secured to the yoke 38 by screws 44, there being a winding 39 on said yoke. The pole pieces 40 and 4! partially surround the rotor 28, with suitable air gaps between rotor and stator for clearance.

The stator pole pieces 40 and 4! may conveniently be alined and supported by the base 2|, which is accomplished in a simple and eflective manner by the pins or studs 42. The yoke 38 may be secured to said pole pieces in any suitable way, as by screws 44 passing through the end portions of the yoke and threaded into the pole pieces or in any other preferred manner. The rotor 28 has a bore 33 extending therethrough in a direction parallel to the shaft 26 and at such radial distance from the said shaft that the bore 43 may be alined with the bore 22 in the base 2|, as shown in Fig. 4. A cylindrical detonator d5, loaded with a sensitive material such as lead azide, for example, is placed in the bore 43.

Electrical conductors leading to the terminals of the winding 39, and other conductors leading to the terminals of the squib Eli of the fuze, are provided. However, three conductors passing out through bore 9 of the wooden block i3 and through a suitable opening 46 in the nose H of the fuze will usually suffice, as one conductor may be used in common by the squib and the stator winding, and may moreover be grounded to the body of the shell.

As shown in Figs. 3 and 4, the inner end 39a of winding 33 is grounded to the core 38, and the outer end 3% of said winding is connected to the metal ring 25. A spring-pressed contact 52, operated by a suitable spring or the like in capsule serves to make contact between conductor 48 and terminal 391) of winding 39 through the ring 25 without regard to angular alinement, so that no precaution is necessary in making the electrical connections to the winding through said contact 52, the other terminal 39a being permanently grounded to the metal body of the projectile I9.

In operation, current from a battery 4'! is supplied through conductors 48 and 49, for example, to the winding 39. This magnetizes the stator 31, with the result that the rotor 23 is turned approximately a quarter turn clockwise, from the position shown in Fig. 3 to that of Fig. 2, until one end of concave portion 34 abuts the pin 35. Initially the rotor is so placed with reference to the stator pole surfaces that the direction of rotation is predetermined, this being accomplished by reason of the smaller air gaps at opposite points P, P, Fig. 3.

The bore 43 is so placed that when the rotor reaches the end of its motion the said bore will be alined with bore 22. Thus, when the rotor is in the position shown in Figs. 2, 4 and 6, the fuze is armed, so that upon detonation of the squib 50 by electricity fed thereto through conductors 53 and 54 from battery 55, the detonation will pass through bore 22, shattering the thin wall 23, and detonating the powder train 4% which in turn will actuate the auxiliary detonator 3, to explode the main charge in the projectile Hi.

It will be obvious that the firing switches and preferably also the batteries, will be located at a safe distance, in a suitable shelter, designated by the dotted line it.

While the device has been disclosed as applied to static firing of explosive shells, it will be clear that it is capable also of other uses, for example, in launching rockets or guided missiles, wherein a propellant or other charge must be ignited while the device is still on the ground, and therefore there is danger of injury to the operating personnel, in case of a premature.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest, an ignition train leading from the squib to the explosive charge of the ammunition, a movably mounted gate initially obstructing said ignition train whereby detonation of the squib is inefiective to explode the charge, and electromagnetic means for moving the gate into non-obstructing position to arm the fuze prior to igniting the said squib.

2. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest, an ignition train leading from the squib to the explosive charge of the ammunition, a rotatably mounted gate initially obstructing said ignition train whereby detonation of the squib is ineffective to explode the charge, and electromagnetic means for turning the gate into non-obstructing position to arm the fuze prior to igniting the said squib.

3. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest, an ignition train leading from the squib to the explosive charge of the ammunition, a rotatably mounted gate initially obstructing said ignition train whereby detonation of the squib is ineffective to explode the charge, said gate having an opening therethrough, and electromagnetic means for rotating the gate into non-obstructing position by bringing said opening into substantial alinement with said ignition train to arm the fuze prior to igniting the said squib.

i. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest, an ignition train leading from the squib to the explosive charge of the ammunition, a rotatably mounted gate initially obstructing said ignition train whereby detonation of the squib is ineffective to explode the charge, said gate having an opening therethrough, an ignition-transmitting means mounted in said opening, and electromagnetic means for rotating the gate into non-obstructing position by bringing said ignitiontransmitting means into substantial alinement with said ignition train to arm the fuze prior to igniting the said squib.

5. A fuzed projectile containing an explosive, and having a detonating squib near said explosive, a gate between the squib and the explosive, said gate having an aperture normally out of alinement with said squib and thus disarming the projectile by preventing the transmission of detonation from the squib to the said explosive, electromagnetic means for moving the gate to aline the aperture with the squib and thus arm the projectile, to explode upon detonation of the squib, and electrical conductors extending from the projectile to a safe location, for energizing said electromagnetic means.

6. A fuzed projectile as defined in claim 5, having additionally a separate second set of electrical conductors and a battery to energize the squib.

'7. In safety firing means for test-detonating squib-actuated fuzed ammunition, an ignition train leading from the squib to the explosive charge of the ammunition, and. electromagnetically operable means for interrupting and completing said ignition train at ,will, said means comprising a stator carrying a magnetizing winding and a rotor mounted to be turned by the magnetic field of the stator, said rotor being interposed in the ignition train and having an aperture that may be alined with said train in one position of said rotor.

8. A safety firing means as defined in claim 7 wherein said rotor is spring-biased to unarmed position, said rotor also being shaped to form a pair of spaced abutments, and wherein a single stop is provided to define the unarmed as well -as the armed position, by abutting respectively against said abutments of said rotor. I

9. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest and having an ignition train leading from the squib to the explosive charge of the ammunition; in combination, a movably mounted gate initially obstructing said ignition train whereby detonation of said squib is ineffective to explode said charge, and electromagnetic means for moving said gate into non-obstructing position to arm said fuze prior to igniting said squib.

10. In safety firing means for test-detonating squib-actuated fuzed ammunition while at rest and having an ignition train leading from the squib to the explosive charge of the ammunition; in combination, a rotatably mounted gate initially obstructing said ignition train whereby detonation of said squib is inefiective to explode said charge, and electromagnetic means for turning said gate into non-obstructing position to arm said fuze prior to igniting said squib.

N 0 references cited. 

